Torque converters include shells and blades to direct fluid flow. Commonly assigned United States patent application publication number 2008/0308373 describes a blade surface with tabs arranged to conform to an inner surface of the shell to provide a fluid seal. United States patent application publication number 2009/0000289 describes a blade with an edge shaped so that at least a portion of the edge can be inserted into a depression in the internal surface of the shell with which it is to be connected. U.S. Pat. No. 5,794,436 assigned to Aisin AW Co., Ltd., describes a pump impeller and a turbine runner with inclined blades having edge portions bent to form right angle connections to shells and cores of the pump impeller and the turbine runner.
The following description is made with reference to 2-4. FIG. 2 is a back view of a prior art impeller assembly shown without brazing for clarity. FIG. 3 is a partial section view of the impeller assembly of FIG. 2 taken generally along line 3-3 in FIG. 2. FIG. 4 is a detail view of encircled region 4 in FIG. 3 shown with brazing. Prior art blade 116 is attached to shells 112 and 114 by braze material. Blade 116 may be attached to shell 112 by braze material 130 and 131, for example. Materials 130 and 131 may be a copper paste melted and bonded to blade 116 and shells 112 and 114 by brazing in a brazing furnace, although other methods and processes are possible. As is known in the art, the strength of a brazing joint is dependent on the gap filled by the braze material. Smaller gaps are desirable as they result in a stronger joint.
A joint area of prior art blade 116 to shell 112 includes gaps 132 and 133 filled by braze material 130 and 131, respectively. Gap 133 is considerably larger than gap 132. Blade thickness 134 is measured between fluid guiding surface 140 and parallel surface 141. As can be appreciated from FIG. 4, as blade thickness 134 is increased or blade to shell angle 136 is decreased, height of surface 138 from shell 112 is increased, thereby increasing gap 133.